Elastic locking ehsert secured



ELASTIC LOCKING INSERT SECURED BY THREAD ROLLING Original Filed July 2,1952 M, 5 flw m J, T w m \A J l P. I F. I \.-.v\ Q #Z w/ m a w. fl W 4\A. a-

a M g m .m V M m F m W F I H 5 H04 w b 5 l E M W 1 1 i 5i 2 ReissuedSept. 28, 1954 ELASTIC LOCKING ENSERT SECURED BY THREAD ROLLING Hugh T.Burdick, Chicago, Ill., assignor to Illinois Tool Works, Chicago, 11L, acorporation of Illinois Original No. 2,663,344, dated December 22, 1953,Serial No. 296,785, July 2, 1952. Application for reissue July 9, 1954,Serial No. 442,220

Matter enclosed in heavy brackets appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

7 Claims.

The present invention relates to self-locking rotary fasteners, such asbolts, screws, studs, and the like. and more specifically relates to theimprovement of a locking bolt, screw, or stud which has an insert whicheffectively locks such devices relative to a complementary threaded nutor equivalent against inadvertent loosening.

A study of locking screws now presently being commercialized, as well asvarious devices of this type which have been patented previously,indicates that a good many of these devices contemplate an articlewhich, from the standpoint of manufacturing, is difiicult orimpracticable. My study also indicates that many of these devices arealso of such a nature that the shank of the fastener is materiallyweakened in order to provide the locking element with its desirableteatures.

Therefore, it is a primary object of this invention to provide a lockingscrew which can be manufactured by well known methods and economicallyproduced.

It is still another object of the invention to provide a locking screwhaving a shank portion provided with one or more locking surfaces whichform continuations of the adjacent surfaces on the threaded convolutionsthereof with the material of the bolt immediately surrounding saidsurface serving as a shoulder to retain the locking surface properlypositioned.

It is still another object of this invention to provide a locking screwof the above type wherein the shoulder'which retains the locking insertproperly positioned is formed during the thread rolling operation sothat the permanent assembly -f the locking insert in the shank of thefastener is accomplished without the necessity of a secondary stakingoperation.

It is still another object of the invention to provide a locking screwwhich, by reason of proper selection of material used to form thelocking insert, retains its effectiveness after long continued orrepeated use.

It is still another object of the invention to provide a method forproducing the fastener contemplated by this invention which assureseconomy in the manufacture of the device which is accomplished withoutthe use of a special machine.

Various other obiects and advantages will become apparent by referenceto the following description and accompanying drawings wherein:

Fig. 1 is a perspective view of a locking screw incorporating theinvention contemplated herein;

Fig. 2 is a side elevational view, partly in section, of a screw blankwith the locking insert mounted therein;

Fig. 3 is a side elevational view, partly in section, taken along theline 3-4 in Fig. 1;

Fig. 4 is a cross sectional view taken along the line 4-! in Fig. 2;

Fig. 5 is a cross sectional view taken along the line 5--5 in Fig. 3;

Fig. 6 is a cross sectional view showing the first step in themanufacture of a locking bolt of the type contemplated by the inventionherein, wherein a recess is provided in the shank of the screw;

Fig. '1 is a cross sectional view of a screw blank "and shows one methodof feeding a plastic insert through the aperture provided foraccommodating same;

Fig. 8 is .a cross sectional view of a fastener showing the cutting ofthe locking insert to proper size;

Fig. 9 is a side view of a locking screw incorporating the inventioncontemplated herein during the thread rolling process which is accom-.

plished by means of conventional rolling dies;

Fig. 10 shows still another embodiment of the invention, wherein alocking screw insert is mounted in a slot adjacent the end of the screwshank and also in proper position in the same manner as the embodimentsshown above;

Fig. 11 is a cross sectional view of the fastener shown in Fig. 10 takenalong the line Il-l I;

Fig. 12 is a longitudinal view of the fastener shown in Fig. 10 takenalong the line l2l2;

Fig. 13 is a side elevational view, partly in section, showing a lockinginsert of the type contemplated by the invention herein disposed at anacute angle relative to the axis of the screw member; and

Fig. 14 is a view similar to Fig. 5 and shows another embodiment whereinthe insert is located to one side 01' the longitudinal axis of the fastener shank.

Referring now to the drawings, wherein like numerals are used to denotecorresponding parts, Fig. 1 shows a locking screw designated generallyby the numeral l0 comprised of a head- 12, a shank portion M, whichshank portion is provided with an aperture i6 adapted to acco'mmodate aplug of resilient material I8; such resilient material being any of thewell known plastic materials, such as nylon, Orion, et cetera. Thematerial used in the fabrication in the plug [8 preferably has aresilient characteristic, which characteristic is present over longperiods of time, and is not materially affected in the temperatureranges for which the locking screw might be subjected, and which hassuch other features as being inexpensive, easy to work with, et cetera,which are so essential in th mass production of such devices.

A very important aspect of the invention contemplated herein resides inthe method contemplated to be used to secure the insert element I8within the confines of the screw shank M. It is contemplated that theselocking inserts can be adequately mounted by subjecting the screw blank14 with the insert I8 mounted therein, as shown in Fig. 2, to a threadrolling operation. The thread rolling process not only forms the helicalthreads I9 on the shank of the screw, but at the same time swages thematerial 20 of the shank I4 adjacently positioned to the periphery ofthe plug into impinging relation therewith, and at the same timecompresses the plug forming at least partial screw threads 2| in the endfaces thereof. Subsequent to the thread rolling operation, and dependentupon the length of the plug is mounted in the stud shank, apredetermined amount of material will extend beyond the valleys andcrests of the surrounding threads formed on the screw blank. Bypredetermining the amount of material desirable to extend beyond thecrest of the screw threads, the locking effectiveness of these lockingfaces is determined and controlled. Tests have beenmade which prove thatthe locking and unlocking torques of this prevailing type of lockingscrew can be closely controlled by selection of the material for theinsert and the amount used in the fabrication of the insert.

In Figs. 6 to 8, inclusive, I have shown one method, and the apparatusto be used with that method, to make the locking screws contemplated bythis invention. In Fig. 6, the screw blank ID has been fed into afixture 22 which is provided with aperture 24 designed to accommodatethe shank of the fastener l0. Ports or entry holes 25 and 28 areprovided and are aligned relative to each other and preferably arrangedto enter the cavity 24 at diametrically opposite sides thereof. Note inFig. 6 that an insert 3|! has been provided to form a hole through whichdrill bit 32 enters the cavity 24. On rotation of the bit, the desiredsize of hole may be made in the fastener shank and the bit thereafterwithdrawn. In Fig. 7, the next step is shown wherein the supply oflocking insert material, such as rod 34, is moved inwardly into theprepared hole of the fastener shank until it extends through the screwblank a predetermined distance. Preferably, The rod 34 is advanced untilits terminal end 35 extends slightly beyond the wall portion 36 and theaperture 24 and into the drill hole 26, as shown in Fig. 7. It should benoted, in Figs. 6, 7, and 8, that the dimension of the aperture 24 isgreater in cross section than the diameter of the fastener shank. Thisdifference in dimension can be of any magnitude and serves to determinethe length of locking insert desired in the particular device. Thislength, as has been previously mentioned, is dependent upon the type ofmaterial to be used and the locking torque desired.

In Fig. 8 is shown the last step in the method designed to prepare thisfastener for the thread rolling operation. Fastener II] is removed fromthe fixture 22 by knockout pin 38, said removal by the pin serving toshear off the locking insert I8 from the rod 34 by reason of theshearing action of the outer surface of the fastener shank I4 and theadjacent wall portion 40 of the fix- 4 ture 22. At the same time, theterminal end 35 of the rod 34 is sheared from the insert I8 by the loweredge of the wall portion 36 of the aperture 24. Thus, the insert I8 iscut to an exact predetermined length.

The fastener blank, with the insert mounted therein, is now fed throughany conventional type of threadrolling machine, which may include threadrolling dies 4| and 42, as shown in Fig. 9. The rolling action deformsthe material 2|] of the shank I4 surrounding the openings of theaperture I6, so that the material 20 is formed into projecttions whichextend into the insert IB and lock it in place. This rolling actionwhich forms the helical threads IS on the screw shank I4 at the sametime formsthe thread segments 2| on the ends of the insert I8. It shouldbe noted that the length of the insert I8 is greater than the diameterof the shank I4, and since the material of the insert is resilient, thethread segments 2| of the insert extend radially outwardly of thethreads l9. In other words, the outer diameter A of the threads I9 isless than the outer diameter B of the thread segments 2|, as shown inFig. 3. Furthermore, the bottoms of the thread segments 2| extendradially outwardly from the bottoms of the threads I9 on the screwshank. Thus, the resilient thread segments 2| will effectively engagethe threads of a complementary threaded fastening device, not shown, tolock the screw l0 against inadvertentloosening. Upon completion of thethread rolling operation, the device is ready for use. The formation ofthe thread segments 2| on the ends of the insert l8 makes theapplication of the fastener 0 to a threaded nut or the like relativelyeasy since it is only necessary for the threads of the nut to compressthe insert and not to cut through it as in a. case where the insert isnot formed with thread segments. Morover, the forming of thread segmentson the insert eliminates the possibility of material being cut from theinsert and jamming the threads of the fastener I0 during its applicationto a complementary fastener element such as a nut.

By reason of the thread rolling operation extruding the metal of thestud inwardly in the vicinity of the marginal edge of the aperture Iiiin the fastener, the staking operation which would normally be necessaryto secure the looking insert is eliminated.

In Figs. 10, 11 and 12, I show still another form of the invention,wherein a screw I0 is provided with a slot 44 adjacent the end oppositethe head of the fastener and a locking insert I 8b of suitable sizemounted therein. This insert, similar to the insert described in theembodiment shown in Figs. 1 to 5, inclusive, has an overall measurementgreater than the length of the slot 44 so that when the thread rollingoperation is performed, a predetermined amount of the material of theinsert extendsv beyond the threadsof the screw's threads. It should benoted that the shoulders 20b extend inwardly to impinge upon the lockinginsert where the threads of the screw blend into the threads of thelocking insert, and, in addition, that during the thread rollingprocess, portions 46 of the shank at the extremity thereof and adjacentthe locking insert are swaged inwardly to trap the insert I82: andpreelude axial movement of the insert relative to the screw shank. Inorder that deformation of the plastic locking insert I8!) is permittedduring the thread rolling operation, in some instances, I have found itadvisable to provide a space 48 behind the insert so that during thethread rolling operation displacement of the insert is permitted andcompression of the insert; can be controlled. This space may be providedby forming the slot 44 with a concave wall, as shown in Fig. 12, oralternatively by forming the insert with a concave inner edge.

' In Fig. 13, I show a lockin screw lllc, wherein the locking insert IBcis disposed at an acute angle relative to the longitudinal axis of thescrew which has the obvious advantage of producing locking surfaces 50and 52 which are axially spaced each from the other along the shank, sothat the locking effect may be obtained for a greater distance along thelength of the screw shank. Another advantage of the device of Fig. 13 isthat the axial spacing of the locking surfaces 50 and 52 tends to tiltor cock the screw with respect to the threads of complementaryfasteners, not shown, whereby there is an increased frictionalresistance between the threads of the screw and the threads of thecomplementary fastener. Furthermore, because the surfaces 5l) and 52 aredisposed at an angle to the axis of the insert 180, the area of theselocking surfaces is increased without weakening the screw by increasingthe size of the aperture into which the insert IE0 is placed. Theportions 200 of the screw shank may be extruded as described above toretain the insert I80.

I also contemplate that where an increase in the amount of lockingsurface of the insert is advantageous, the aperture provided in thescrew shank for accommodating the insert can be located at one side ofthe diameter of the screw. This structure is shown in Fig. 14, whereinthe insert. id is located at one side of the longitudinal axis of thefastener shank Md. By this arrangement, the opposite openings in theexternal wall in the screw have a larger cross sectional area than thecross sectional area of the hole itself when determined mathematicallyby the formula 1r1 and, thus, the area of the ends or looking surfacesof the insert l8d is larger than the diameter of the insert. This hasthe obvious advantage over enlarging the size of ehe aperture drilled inthe screw in that the desired increase of locking surface can beprovided without weakening the shank of the screw. Furthermore, bylocating both locking surfaces or ends of the insert lBd on one side ofthe center line of the shank Md, the insert which will engage one sideof a complementary fastener, not shown, will tend to force the shankagainst the opposite side of the complementary fastener and, thereby,incicase the frictional resistance between the threads of the shank andthe threads of the fastener. As before, the portions 20d of the shankare extruded during the thread rolling operation to retain the insert.

From the foregoing description, it is seen that the present inventionhas provided a simple, yet highly efficient, self-locking fastener whichmay be rapidly and economically manufactured. Moreover, the novel methodset forth herein makes it possible to form the thread and secure theinsert in one step, which not only has the obvious advantage ofeliminating the conventional secondary staking operation, but alsoeliminates the possibility of damage to the threads which might occurduring such a secondary staking operation.

While specific embodiments of the "invention are hereinabove describedand shown, it is to be understood that I do not intend to be limited tothe constructions and methods illustrated and described, but limitedonly by the following claims.

I claim:

1. A self-locking rotary fastener including an elongated shank havingrolled screw threads on a peripheral surface thereof, said shank havin arecess therein opening at said peripheral surface so as to intersectthread convolutions on said shank, and an insert of deformable materialmounted within said recess and presenting an ex A 2. A self-lockingrotary fastener as set forth in claim 1, wherein the recess whichaccommodates the insert completely traverses the screw shank to providea pair of peripheral locking sec tions.

3. A self-locking rotary fastener as set forth in claim 1, wherein therecess which accommodates the insert extends transversely of and at anacute angle to the axis of the screw member so as to increase theexposed peripheral area of the insert.

4. A self-locking rotary fastener as set forth in claim 1, wherein therecess which accommodates the insert extends transversely of the screwshank and substantially laterally with respect to the screw axis so asto increase the exposed peripheral area of the insert.

5. The method of producing a self-locking threaded rotary fastener froman elongated unthreaded shank, which includes forming an opening in theunthreaded shank transverse to the longitudinal axis thereof, placing aninsert of deformable material into said opening of greater length thanthe length of said opening so that one end of the insert extendsradially from said shank, and thereafter thread rolling the shank toform threads in the shank and said end of the insert and simultaneouslydeforming portions of said shank surrounding said opening inwardlyagainst said insert to retain the insert in mounted position in saidshank.

6'. The method of producing a self-locking threaded rotary fastener froman elongated unthreoded shank, which includes forming an aperturecompletely through the unthreaded shank transverse of the longitudinalaxis thereof, placing an insert of deformable material into saidaperture with opposite ends of the insert extendmy oppositely from theaperture, thereafter thread rolling the shank to form helical threadsthereon and thread segments in the opposite ends of the insert, andsimultaneously deforming portions of said shank surrounding saidaperture at opposite sides of said shank inwardly against said insert toretain the insert in assembled relationship within said aperture. y

7. The method of producing a self-locking threaded rotary fastener froma fastener blank having an elongated unthreaded shank, which shank has adeformable insert disposed in a radially opening recess therein with anend of the insert extending radially from the recess, comprising thread.rolling the shank to form helical threads thereon and thread segments onsaid insert end, and simultaneously deforming portions of said shanksarrOunding said recess inwardly against said insert to retain theinsert in preassemb'led relationship with said shank.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS Number Number Name Date Furlan Dec. 16, 1924 StollDec.'l0, 1940 Boots Jan. 30, 1951 Brutus Aug. 26, 1952 FOREIGN PATENTSCountry Date Great Britain May 9, 1932 Great Britain Dec. 2, 1938

